Selective light-blocking optical products having a neutral reflection

ABSTRACT

Optical products that comprise a composite coating having multiple bilayers of a first layer and a second layer, each provided with a binding group component which together form a complementary binding group pair, the multiple bilayers comprising: at least one bilayer a) comprised of a first pigment or pigment blend that exhibits a color reflection value that is less than about 2.5; at least one bilayer b) comprised of a pigment or pigment blend that selectively blocks visible light in a wavelength range of interest; and at least one bilayer c) comprised of a second pigment or pigment blend that exhibits a color reflection value that is less than about 2.5, wherein the optical product selectively blocks visible light in the wavelength range of interest, while exhibiting a color reflection value that is less than about 2.5.

FIELD OF THE INVENTION

The present invention broadly relates to optical products for use, forexample, in automotive and architectural window applications. Moreparticularly, the invention relates to optical products that provideselective light blocking while maintaining a desired neutral reflection.

BACKGROUND OF THE INVENTION

Light and energy blocking and color correction have typically beenimparted to optical products such as solar control films by use oforganic dyes. More particularly, current commercial practice forproducing dyed film from polyester includes swelling of the molecularstructure of the polyester in baths of hot organic solvent such asethylene glycol during the dyeing process, as swelled polyester(particularly PET) films are capable of absorbing organic dyes. Thesefilms and their manufacturing processes suffer many drawbacks. Forexample, only a limited number of organic dyes are soluble and stable inthe hot solvent swelling media used in the dyeing process and many ofthose are subject to degradation by high energy radiation (sub-400 nmwavelength) to which the substrate is subjected when used in window filmapplications, thereby shortening the useful lifetime of the product.Further, the dye typically permeates the entire thickness of the filmsuch that there is no way to separate the filtration or blockingfunction of the film from its visible reflection, that is, from itsexternal appearance.

To address some of these drawbacks, some film manufacturers havetransitioned to using a pigmented layer on the surface of a basepolymeric film for tinting a polymeric film. For example, U.S. PublishedApplication number 2005/0019550A1 describes color-stable, pigmentedoptical bodies comprising a single or multiple layer core having atleast one layer of an oriented thermoplastic polymer material havingdispersed within it a particulate pigment. Such products can suffer amyriad of processing and performance drawbacks. For example, layers ofthis type are typically applied as thin films and require a relativelyhigh pigment concentration to achieve a desired tint level, particularlyin automotive window films with a relatively high desired level ofdarkening. These high pigment concentrations are difficult to uniformlydisperse within the thin layer. And again, it may be difficult toseparate the desired blocking properties of the product from itsexternal appearance or reflection since the pigment is dispersedthroughout the thickness of the thermoplastic polymer material.

More recently, layer-by-layer films have been developed to providesimilar functionalities. Processes of making these films take advantageof charge-charge, hydrogen bonding, or other complementary interactionsto assemble successive layers. This requires the use of solvents,typically water, to ionize molecules or support hydrogen donation andacceptance in the deposition solutions.

For example, U.S. Pat. Nos. 9,453,949 and 9,891,357, assigned to theassignee of the present application, the disclosures of which areincorporated herein by reference, disclose layer-by-layer compositefilms that include electromagnetic energy-absorbing insoluble particlesthat may be selected to provide pigmentation, UV-absorption, and/orIR-absorption properties. Likewise, U.S. Pat. No. 9,395,475, thedisclosure of which is incorporated herein by reference, discloseslayer-by-layer integrated stacks that serve as optical filters.

Optical products are known that can selectively block certainwavelengths of light, for example blue light that is believed tocontribute to macular degeneration, cataracts, and the like. Forexample, shooting glasses having lenses containing yellow dyes are knownto block blue light, but have a clearly discernible yellow tint to boththe user and the observer. U.S. Pat. No. 8,882,267 discloses ophthalmicand nonophthalmic systems that are said to provide an averagetransmission of 80% or better transmission of visible light, to inhibitselective wavelengths of blue light, to allow for the wearer's propercolor vision performance, and to provide a mostly color neutralappearance to an observer looking at the wearer wearing such a lens. Thesystems are said to be color balanced such that the yellow or ambercolor, or other unwanted effect of blue blocking is reduced, offset,neutralized or otherwise compensated for, so as to produce acosmetically acceptable result, without at the same time reducing theeffectiveness of the blue blocking.

A continuing need exists in the art for electromagnetic energy-absorbingoptical products, and especially window films, that selectively filterbands of energy from transmitted visible light, producing a distincttransmitted color, while remaining relatively neutral in reflectedcolor.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to optical products that comprise acomposite coating, deposited on a substrate, that includes multiplebilayers having a first layer and a second layer, each provided with abinding group component which together form a complementary bindinggroup pair. According to this aspect, the multiple bilayers comprise, insequence: at least one bilayer a) comprised of a first pigment orpigment blend that, when formed into a bilayer, exhibits a colorreflection value that is less than about 2.5; at least one bilayer b)comprised of a pigment or pigment blend that, when formed into abilayer, selectively blocks visible light in a wavelength range ofinterest; and at least one bilayer c) comprised of a second pigment orpigment blend that, when formed into a bilayer, exhibits a colorreflection value that is less than about 2.5, and that may be the sameas or different than the first pigment or pigment blend. In this aspect,the optical product selectively blocks visible light in the wavelengthrange of interest, while exhibiting a color reflection value that isless than about 2.5, as defined elsewhere herein.

In various aspects, the wavelength range of interest may be, forexample, a 75 nm wavelength range, or a 50 nm wavelength range, or asdescribed elsewhere. Similarly, in various aspects, the wavelength rangeof interest may be from 400 nm to 450 nm, or from 600 nm to 650 nm, orfrom 500 nm to 600 nm, or from 525 nm to 575 nm, or as describedelsewhere herein.

In one aspect, the optical products of the invention may furthercomprise at least one bilayer d), deposited on the at least one bilayerc), comprised of a pigment or pigment blend that, when formed into abilayer, selectively blocks visible light in the wavelength range ofinterest, and that may be the same as or different than the pigment orpigment blend of bilayer b); and at least one bilayer e) comprised of aneutral pigment or pigment blend that, when formed into a bilayer,exhibits a color reflection value that is less than about 2.5, and thatmay be the same as or different than the pigment or pigment blend ofbilayer, a) or bilayer c).

In various aspects, the optical products of the invention may have acolor reflection value of less than about 2.0, or less than about 1.5,or as described elsewhere herein.

In further aspects, the optical products of the invention may block atleast 70% of visible light within the wavelength range of interest, orat least 80% of visible light within the wavelength range of interest,or as described elsewhere herein.

In one aspect, the substrate of the optical products of the inventionmay comprise a polyethylene terephthalate film, and separately, thecomposite coating may have a total thickness of from 5 nm to 1000 nm.

The optical products of the invention may be in the form of a windowfilm that is applied to a vehicle, for example an automobile, anaircraft, or a boat. Similarly, the optical products of the inventionmay be in the form of a window film applied to a building, or may be acomposite interlayer for laminated glass.

In other aspects, the optical products of the invention may have avisible light transmission of no less than 40%, or no less than 60%, oras described elsewhere herein.

Further aspects of the invention are as disclosed and claimed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail below, and withreference to the accompanying drawings, wherein like reference numeralsthroughout the figures denote like elements and wherein:

FIG. 1 is a plot of the percent of light absorbed over the visiblewavelength range of thin films made from five pigments that are usefulaccording to the invention.

FIG. 2 is a plot of the percent of light reflected over the visiblewavelength range of thin films made from five pigments that are usefulaccording to the invention.

FIG. 3 is a plot of the percent of light reflected over the visiblewavelength range of a thin film made from a blend of three pigments thatis relatively neutral in reflectance across the visible spectrum.

FIG. 4 is a plot of the amount of light reflected along the visiblespectrum for 2, 4, 6, and 8 layers of a yellow pigment useful accordingto the invention.

FIG. 5 is a schematic drawing that depicts a window film that is oneembodiment of the present invention.

FIG. 6 is a plot of the percent of reflection of wavelengths along thevisible spectrum for three films prepared in the examples.

FIG. 7 is a plot of the percent transmission of wavelengths along thevisible spectrum for three films prepared in the examples.

FIG. 8 is a plot of the percent transmission of wavelengths along thevisible spectrum for two films prepared in the examples.

FIG. 9 is a plot of the percent transmission of wavelengths along thevisible spectrum for two films prepared in the examples.

DETAILED DESCRIPTION

According to the invention, optical products are provided thatselectively block visible light in a wavelength range of interest,producing a distinct transmitted color, while remaining relativelyneutral in reflected color. This is distinguished from light-filteringoptical products in which residual color from a light-filteringfunctionality provided in the optical product results in a non-neutralreflection, that is, a reflection that is perceived by the eye as beingcolored.

In one aspect, then, the invention relates to pigmented optical productsthat selectively block visible light in a wavelength range of interest,for example a 50 nm wavelength range, while exhibiting a colorreflection value, as defined herein, that is less than about 2.5.

In another aspect, the optical products of the invention block at leastabout 70% of visible light in a wavelength range of interest, whileexhibiting a color reflection value, as defined herein, that is lessthan about 2.5.

According to the invention, optical products are provided that comprisecomposite coatings, deposited on a substrate, for example a polymericsubstrate. These composite coatings comprise multiple bilayers thatinclude a first layer and a second layer, each provided with a bindinggroup component which together form a complementary binding group pair.

In one aspect, the multiple bilayers may comprise, in sequence: at leastone bilayer a) comprised of a neutral pigment or pigment blend that,when mixed together and formed into a bilayer, exhibits a colorreflection value that is less than about 2.5; at least one bilayer b)comprised of a pigment or pigment blend that, when mixed together andformed into a bilayer, selectively blocks visible light in a wavelengthrange of interest; and at least one bilayer c) comprised of a neutralpigment or pigment blend that, when formed into a bilayer, exhibits acolor reflection value that is less than about 2.5, and that may be thesame as or different than the bilayer a), wherein the optical productselectively blocks visible light in a wavelength range of interest,while exhibiting a color reflection value that is less than, forexample, about 2.5.

When we say that the optical product or film, or an individual bilayeror plurality of bilayers, selectively blocks visible light within awavelength range of interest, or within a defined wavelength range, or apredetermined wavelength range, we mean that the amount of light blockedwithin that wavelength range is greater than the amount of light blockedat other wavelength ranges of the same width within the visible lightspectrum, which is defined herein for purposes of the invention as beingfrom 400 nm to 700 nm. When we say that the light is selectivelyblocked, the definition of “blocked” is intended to encompass the lightabsorbed and the light reflected, as well as any light within thewavelength range that is scattered by the optical product; that is, alllight that is not transmitted through the film or optical product sothat it can be measured is considered to be “blocked,” whether the lightblocked is absorbed, reflected, or scattered. The wavelength of interestcan, of course, be predetermined, and a pigment selected, for example,that absorbs light within that preselected or predetermined wavelengthrange. Conversely, the wavelength range of interest may be randomlyselected, in the sense that pigments may be tried for novelty oresthetic effect and chosen based solely on appearance and their effecton transmitted color, so long as the desired relatively neutralreflection is also achieved, as defined by the color reflection value.

We note that generally-accepted definitions of the wavelength range ofvisible light, as well as the definitions of perceived colors and thewavelengths of light within which the colors are perceived, are somewhatapproximate. Further, the range within the visible spectrum that lightaccording to the invention is selectively blocked will be, in part, afunction of the type of light-filtering functionality provided to theoptical products of the invention, for example the nature of the pigmentparticle(s) themselves, as well as the part of the visible lightspectrum that is intended to be blocked, since different “colors” areperceived over varying wavelength ranges of light. For example, lightperceived as red may be broadly and somewhat arbitrarily defined aslight having a wavelength range as broad as from about 620 nm to about750 nm (that is, partly outside the visible spectrum althoughperceivable by some individuals), a wavelength range of about 130 nm.Further, certain definitions of blue color (and especially those inwhich violet is defined within a separate wavelength range) are definedas having a wavelength range as narrow as from about 450 nm to about 495nm, while other definitions of blue-colored light extend from 400 nm to500 nm. The wavelength ranges of interest that are selectively blockedaccording to the invention are thus a function of the part of thevisible wavelength range that is blocked, as well as the fundamentalproperties of the pigment(s) used to selectively block the light,especially the absorptive properties, as well as any interferenceproperties of the film that may be a function of the thickness of theindividual first or second layers, or the two layers that together forma bilayer.

Thus, according to the invention, the wavelength ranges of visible lightwhich the optical products of the invention selectively block may be,for example, as narrow as a 25 nm wavelength range, or may be a 30 nmwavelength range, or a 40 nm wavelength range, or a 50 nm wavelengthrange, or a 60 nm wavelength range, or a 75 nm wavelength range, or a100 nm wavelength range. In a broad aspect, the defined wavelength rangeof interest is a range in which the amount of light selectively blockedis greater than the amount blocked in any other visible wavelength rangeof the same width, with the visible wavelength range of light as definedherein being from 400 nm to 700 nm. Thus, in one aspect, the amount oflight within the wavelength range of interest that is selectivelyblocked may be defined with respect to other ranges of the same width,such that the amount of visible light blocked within the wavelengthrange of interest is greater than the amount of visible light blockedwithin any other range of the same width in the visible light spectrum.

Further, the amount of light selectively blocked within the wavelengthrange of interest may also be defined in absolute terms. That is, theamount of light blocked within the wavelength range of interest may beat least 25%, or at least 35%, or at least 50%, or may be even higher,if desired, for example at least 60%, or at least 70%, or at least 75%,or at least 80%.

In various aspects, the wavelength range of interest may be, forexample, from 400 nm to 450 nm, or from 450 nm to 500 nm, or from 500 nmto 550 nm, or from 550 nm to 600 nm, or from 580 nm to 700 nm, or from500 nm to 600 nm, or from 525 nm to 575 nm, or as defined elsewhereherein. While some of the wavelength ranges just cited are 50 nmwavelength ranges, other wavelength ranges may be selected, as describedhere and elsewhere herein.

Similarly, the overall amount of visible light transmitted, or T_(vis),may likewise vary widely. Thus, the T_(vis) of the optical products ofthe invention may be at least 20%, or at least 30%, or at least 50%, orat least 60%, or at least 75%, or at least 80%, or alternatively may beno more than 10%, or no more than 20%, or no more than 30%, or asdefined elsewhere herein.

The light measurements, as used herein, are those determined using the1976 CIE L*a*b* Color Space. CIE L*a*b* is an opponent color systembased on the earlier (1942) system of Richard Hunter called L, a, b. Inthe CIE L*a*b* color space, the three coordinates represent: thelightness of the color (L*=0 yields black and L*=100 indicates diffusewhite); its position between red and green (a*, negative values indicategreen while positive values indicate red); and its position betweenyellow and blue (b*, negative values indicate blue and positive valuesindicate yellow).

As used herein, the color reflection value is calculated from theformula sqrt[(a*)²+(b*)²]. For example, the color reflection value of anoptical product or a bilayer having a reflective a* value of 0.5 and areflective b* value of −0.5 would be 0.71, which is relatively neutral,while an optical product having a reflective a* value of 1.5 and areflective b* value of −1.5 would have a color reflection value of 2.1which, while still relatively neutral, is less neutral than the opticalproduct having a color reflection value of 0.71. Relatively neutralcolor reflection values according to the invention, whether those usedto describe the finished optical products or the pigment or pigmentblends that comprise individual bilayers, are those that are less thanabout 5, or less than 4, or less than or equal to 3, and especiallyvalues that are less than about 2.5, or less than about 2, or less thanor equal to 1.5. Thus, the lower the color reflection value, the moreneutral is the perceived color. So far as we are aware, this colorreflection value and the formula for determining it have not been usedpreviously, although the values used to calculate this color reflectionvalue are generally-accepted measured values using the 1976 CIE L*a*b*Color Space, that is the a* and b* values, and as a practical matter areprobably the most common way of defining color that is in use today.

The color reflection value just described is thus used according to theinvention to determine whether the optical products of the inventionhave a suitably neutral reflection. The measurement is also used hereinto determine the suitability of the pigment or pigment blends used inindividual bilayers or a plurality of bilayers of the same pigmentcomposition. In this measurement, a bilayer or plurality of bilayers isformed from the pigment or pigments on a suitable substrate, as furtherdescribed herein, and a measurement obtained.

According to various aspects of the invention, optical products are thusprovided that comprise composite coatings, deposited on a substrate, forexample a polymeric substrate. These composite coatings comprisebilayers that include a first layer and a second layer, each providedwith a binding group component which together form a complementarybinding group pair. In one aspect, the multiple bilayers may comprise,in sequence: at least one bilayer a) comprised of a neutral pigment orpigment blend that, when formed into a bilayer, exhibits a colorreflection value that is less than about 2.5; at least one bilayer b)comprised of a pigment or pigment blend that, when formed into abilayer, selectively blocks visible light in a wavelength range ofinterest; and at least one bilayer c) comprised of a neutral pigment orpigment blend that, when formed into a bilayer, exhibits a colorreflection value that is less than about 2.5, and that may be the sameas or different than the pigment or pigment blend of the bilayer a).According to this aspect, the optical product just described selectivelyblocks visible light in a wavelength range of interest, while exhibitinga relatively low color reflection value that may be, for example, lessthan about 2.5.

Those skilled in the art will readily appreciate that furtheralternating bilayers of similar character may be added in sequence, suchthat the optical product may further comprise, for example deposited onbilayer a) or bilayer c): d) at least one bilayer comprised of a pigmentor pigment blend that, when formed into a bilayer, selectively blocksvisible light in the wavelength range of interest, and that may be thesame as or different than the pigment or pigment blend of the bilayerb); and e) at least one bilayer comprised of a neutral pigment orpigment blend that, when formed into a bilayer, exhibits a colorreflection value that is less than about 2.5, and that may be the sameas or different than the pigment or pigment blend of the bilayer a) andthe bilayer c).

When we say that the bilayers described in a) and c), and in optionalbilayer e), above are comprised of a neutral pigment or pigment blend,we mean that the nature of the pigment or pigments is such that thereflectance of a bilayer or plurality of bilayers formed from them isrelatively neutral, as defined by the color reflection value alreadydescribed. That is, in determining whether a neutral pigment or pigmentblend is suitable for use according to the invention, the pigment orpigments are formed into a bilayer on a suitable substrate and the colorreflection value is determined. The measurement is thus taken, forpurposes of determining whether a given pigment or pigment blend issuitable for use according to the invention, on an isolated bilayer orbilayers, and not as incorporated into the finished optical product.

Similarly, with respect to the at least one bilayer b), and optionalbilayer d), when determining whether a pigment or pigment blend issuitable for use according to the invention, a bilayer or plurality ofbilayers is formed from the pigment or pigments, and the ability of thebilayer to selectively block visible light in a wavelength range ofinterest is determined. The measurement is thus taken, for purposes ofdetermining whether a given pigment or pigment blend is suitable toselectively block visible light in a wavelength range of interest, on anisolated bilayer or plurality of bilayers, and not on the finishedoptical product. We note, however, that the color reflection value ofthe finished optical product is also determined in the same way.

Thus, when selecting a neutral pigment or pigment blend for useaccording to the invention, the measured color reflection value of anindividual bilayer a) or c) or e) is considered, or a plurality ofbilayers a) or c) or e), as the case may be. This color reflection valuemay vary slightly based on the number of bilayers of each of the twotypes of bilayers a) and c) and e) present, but any number of bilayersmay be used according to the invention, so long as the measured colorreflection value of a bilayer or plurality of bilayers formed from thepigment(s) is within the desired range.

The value of a measured color reflection value will also vary, whenmeasured on a finished optical product, based on the nature of thebilayer b), and optional bilayer d), including the nature of the pigmentitself and the number of bilayers in the at least one bilayer b) or d).Thus, the neutrality of the bilayers a) and c) and e) are defined hereinbased on measurements of the bilayers or plurality of bilayers a) and c)and e) themselves, in the absence of bilayer b) or d), while the overallneutrality of the optical product obtained is based on the colorreflection value of the final optical product itself. In this aspect,the composite coating may be considered a sandwich structure, or aninterleaved structure, in which bilayer b) or d), comprised of a pigmentor pigment blend that selectively blocks visible light in a wavelengthrange of interest, is sandwiched between bilayers a) and c) or c) ande), as the case may be, comprised of a neutral pigment or pigment blendthat may be the same as or different from one another. These sandwichedor interleaved composite coating structures thus comprise at least onea) bilayer, one b) bilayer, and one c) bilayer, for a total of at leastthree bilayers, and optionally additional bilayers, for example bilayersd) and e) as just described.

In various aspects, the present invention is thus directed to opticalproducts comprising a polymeric substrate provided thereon with acomposite pigment coating. The composite pigment coatings are comprisedof at least a first layer and a second layer which together form asingle bilayer, at least one of which layers comprises or includes apigment or pigment blend. Preferably, the first layer is immediatelyadjacent the substrate and a second layer is immediately adjacent to thefirst layer which was applied to or deposited on the substrate. Each ofthe first and second layers together thus form a bilayer. One or moreadditional first and second layers may thus be used to form a pluralityof bilayers. Each of these bilayers or the plurality of bilayers takentogether may also be described herein as a bilayer system, a compositecoating, or an LbL (layer-by-layer) coating. As described, each of thebilayers can be the same or different.

According to the invention, the composite pigment coating comprises alayer-by-layer coating that includes one or more pigments. Each of thelayers of a given bilayer may comprise a polyionic binder, an insolublepigment particle, or both. Each layer of the bilayer(s) includes abinding group component with the binding group component of the firstlayer and the binding group component of the second layer constituting acomplementary binding group pair. As used herein, the phrase“complementary binding group pair” means that binding interactions, suchas electrostatic binding, hydrogen bonding, Van der Waals interactions,hydrophobic interactions, and/or chemically-induced covalent bonds arepresent between the binding group component of the first layer and thebinding group component of the second layer of the composite coating. A“binding group component” is a chemical functionality that, in concertwith a complementary binding group component, establishes one or more ofthe binding interactions described above. The components arecomplementary in the sense that binding interactions are created throughtheir respective charges.

According to the invention, the binding group component may be provided,for example, through a polyionic binder or a pigment. That is, if aselected pigment is charged, for example, so that it can serve as abinding group component of a given layer of the bilayer system, thenthat pigment may be used alone to form a layer of the bilayer. If thepigment does not include a binding group component, then that pigmentmay be combined with a molecule having a binding group component, forexample a polyionic binder, to form a bilayer. We note that not everybilayer of the bilayer system need include a pigment, but according tothe invention, those bilayers that include a pigment may have either acharged pigment or an uncharged pigment, or both.

According to the invention, a layer of the composite pigment coating maythus include a polyionic binder, which is defined as a macromoleculecontaining a plurality of either positively- or negatively-chargedmoieties along the polymer. Polyionic binders with positive charges areknown as polycationic binders while those with negative charges aretermed polyanionic binders. Also, it will be understood by one ofordinary skill that some polyionic binders can function as either apolycationic binder or a polyanionic binder, depending on factors suchas pH, and are known as amphoteric. The charged moieties of thepolyionic binder constitute the “binding group component” of a givenlayer.

Suitable polycationic binder examples include poly(allylaminehydrochloride), linear or branched poly(ethyleneimine),poly(diallyldimethylammonium chloride), macromolecules termedpolyquaterniums or polyquats and various copolymers thereof. Blends ofpolycationic binders are also contemplated by the present invention.

Suitable polyanionic binder examples include carboxylic acid-containingcompounds such as poly(acrylic acid) and poly(methacrylic acid), as wellas sulfonate-containing compounds such as poly(styrene sulfonate) andvarious copolymers thereof. Blends of polyanionic binders are alsocontemplated by the present invention. Polyionic binders of bothpolycationic and polyanionic types are generally known to those ofordinary skill in the art and are described, for example, in U.S.Published Patent Application number US20140079884 to Krogman et al,incorporated herein by reference. Examples of suitable polyanionicbinders include polyacrylic acid (PAA), poly(styrene sulfonate) (PSS),poly(vinyl alcohol) or poly(vinylacetate) (PVA, PVAc), poly(vinylsulfonic acid), carboxymethyl cellulose (CMC), polysilicic acid,poly(3,4-ethylenedioxythiophene) (PEDOT) and combinations thereof withother polymers (e.g. PEDOT:PSS), polysaccharides, and copolymers of theabove mentioned. Other examples of suitable polyanionic binders includetrimethoxysilane functionalized PAA or PAH or biological molecules suchas DNA, RNA or proteins. Examples of suitable polycationic bindersinclude poly(diallyldimethylammonium chloride) (PDAC), Chitosan,poly(allyl amine hydrochloride) (PAH), polysaccharides, proteins, linearpoly(ethyleneimine) (LPEI), branched poly(ethyleneimine) BPEI andcopolymers of the above-mentioned, and the like. Examples of polyionicbinders that can function as either polyanionic binders or polycationicbinders include amphoteric polymers such as proteins and copolymers ofthe above mentioned polycationic and polyanionic binders.

The concentration of the polyionic binder in the first layer may beselected based in part on the molecular weight of its charged repeatunit but will typically be between 0.1 mM-100 mM, more preferablybetween 0.5 mM and 50 mM, and most preferably between 1 and 20 mM basedon the molecular weight of the charged repeat unit.

According to the invention, if the binding group component of a givenlayer includes a negatively-charged pigment, then the polyionic binderof a complementary layer will typically be a polycationic binder, suchas polyallylamine hydrochloride. The polyionic binders will typically besoluble in water and the composition used to form the layer will be anaqueous solution of polyionic binder. In an embodiment wherein thepolyionic binder is a polycation and the first layer is formed from anaqueous solution, the pH of the aqueous solution may be selected so thatfrom 5 to 95%, preferably 25 to 75%, and more preferably approximatelyhalf of the ionizable groups are protonated. Other optional ingredientsin the first layer include biocides or shelf-life stabilizers.

It will be understood that when the first layer of a bilayer comprises apolycationic binder, the second layer may comprise a polyanionic binderor a negatively-charged insoluble pigment particle, or both. Of course,additional functionality may be provided to the optical products of theinvention in the composite pigment coating. For example, one or more ofthe layers will typically be provided with electromagneticenergy-absorbing insoluble pigment particles, which themselves may becharged particles. The phrase “electromagnetic energy-absorbing” meansthat the particle is purposefully selected as a component for theoptical product for its preferential absorption at particular spectralwavelength(s) or wavelength ranges(s). The term “insoluble” is meant toreflect the fact that the particle does not substantially dissolve inthe composition used to form a given layer and exists as a particle inthe optical product structure. Of course, the term electromagneticenergy-absorbing insoluble particles encompasses pigments; however,insoluble particles such as UV absorbers or IR absorbers, or absorbersin various parts of the electromagnetic spectrum that do not necessarilyexhibit color, are also within the term and may be provided according tothe invention.

Pigments suitable for use according to the invention are preferablyparticulate pigments with an average particle diameter from about 5 toabout 300 nanometers, or from 10 to 100 nanometers, often referred to inthe art as nanoparticle pigments, although there is not necessarily anupper limit to the particle size in those cases where a larger particlesize may perform well in the LbL processes useful according to theinvention. In one aspect, the surface of the pigment includes thebinding group component of a given layer. Suitable pigments areavailable commercially as colloidally-stable water dispersions frommanufacturers such as Cabot, Clariant, DuPont, Dainippon and DeGussa.Particularly suitable pigments include those available from CabotCorporation under the Cab-O-Jet® name, for example 250C (cyan), 265M(magenta), 270Y (yellow), 554B (blue), 1027R (red), or 352K (black). Inorder to be stable in water as a colloidal dispersion, the pigmentparticle surface is typically treated to impart ionizable characterthereto and thereby provide the pigment with the desired binding groupcomponent on its surface. It will be understood that commerciallyavailable pigments are sold in various forms such as suspensions,dispersions and the like, and care should be taken to evaluate thecommercial form of the pigment and modify it as/if necessary to ensureits compatibility and performance with the optical product components,particularly in the embodiment wherein the pigment surface alsofunctions as the binding group component of the second layer.

Multiple pigments or pigment blends will be utilized to achieve theselective blocking of visible light with relatively neutral reflection,as already described. However, it will again be understood that, shouldmultiple pigments be used, they should be carefully selected to ensuretheir compatibility and performance both with each other and with theoptical product components. This is particularly relevant in theembodiment wherein the pigment surface also functions as the bindinggroup component of the layer, as for example particulate pigments canexhibit different surface charge densities due to different chemicalmodifications that can impact compatibility.

One or more of the layers of the LbL composite pigment coating mayfurther include a screening agent that promotes even and reproducibledeposition of the layer via improved dispersion of the pigment orpolyionic binder within the layer by increasing ionic strength andreducing interparticle electrostatic repulsion. Screening agents areknown to those of ordinary skill in the art and are described forexample in U.S. Published Patent Application number US20140079884 toKrogman et al. Examples of suitable screening agents include lowmolecular weight salts such as halide salts, sulfate salts, nitratesalts, phosphate salts, fluorophosphate salts, and the like. Examples ofhalide salts include chloride salts such as LiCl, NaCl, KCl, CaCl₂,MgCl₂, NH₄Cl and the like, bromide salts such as LiBr, NaBr, KBr, CaBr₂,MgBr₂, and the like, iodide salts such as LiI, NaI, Kl, Cal₂, Mgl₂, andthe like, and fluoride salts such as, NaF, KF, and the like. Examples ofsulfate salts include Li₂SO₄, Na₂SO₄, K₂SO₄, (NH₄)₂SO₄, MgSO₄, CoSO₄,CuSO₄, ZnSO₄, SrSO₄, Al₂(SO₄)₃, and Fe₂(SO₄)₃. Organic salts such as(CH₃)₃CCl, (C₂H₅)₃CCl, and the like are also suitable screening agents.Sodium chloride is typically a preferred screening agent based oningredient cost. The presence and concentration level of a screeningagent may allow for higher loadings of the pigment or the binder such asthose that may be desired in optical products with a T_(vis) of no morethan 50% and also may allow for customizable and carefully controllableloadings in order to achieve customizable and carefully controllableoptical product T_(vis) levels.

Suitable screening agent concentrations can vary with salt identity andare also described for example in U.S. Pat. No. 9,387,505 to Krogman etal, incorporated herein by reference in its entirety. In someembodiments, the screening agent concentration can range between 1 mMand 1000 mM or between 10 mM and 100 mM or between 30 mM and 80 mM. Insome embodiments the screening agent concentration is greater than 1 mM,10 mM, 100 mM or 500 mM.

The layers of the composite pigment coating may also contain otheringredients such as biocides or shelf-life stabilizers.

As noted, the composite pigment coatings of the invention may comprise aplurality of bilayers that may be the same or different. For example, anoptical product of the invention may include first and second bilayers,each with a first layer and a second layer. For embodiments with aplurality of bilayers, it will be appreciated that the binders orpigments for each of the layers of a bilayer may be independentlyselected and that the layers containing pigment, for example, will incombination provide an additive effect to the user of the opticalproduct. This additive effect can be customized and carefully controlledin part by the concentration of the pigment particles in each of thelayers used as dispersed through the presence of the screening agent.For example, pigmented layers will, in combination, provideapproximately an additive effect on the user's visually perceived color,that is, on the transmission of the film. In embodiments in which aplurality of bilayers is provided that include pigments, the pigmentsfor each of the layers may be of the same or similar composition and/orcolor such that the additive effect is to increase intensity or depth ordarkness of the visually perceived transmission of the optical productor, stated another way, to reduce electromagnetic transmittance in thevisible wavelength range (or T_(vis)).

In one embodiment, carbon black may be used as a pigment for at leastone layer, for example a layer in which the reflection is intended to berelatively neutral as evidenced by its color reflection value.Similarly, blends of pigments such as those discussed herein may be usedtogether to obtain a bilayer or plurality of bilayers having arelatively neutral reflection. Pigments such as those listed above canalso be used alone or as blends to obtain a bilayer or a plurality ofbilayers that selectively block visible light in a wavelength range ofinterest. In general, the additive effect of multiple bilayers to theuser is a visually perceived darkened color, reducing electromagnetictransmittance in the visible wavelength range (or T_(vis)). As discussedabove, the present invention may be useful in products whereinrelatively high levels of darkening are desired. Accordingly, in oneembodiment, the optical products of the present invention have a T_(vis)of no more than 50%, or no more than 70%.

FIG. 1 depicts the percent of light absorbed over the visible wavelengthrange of five different pigments formed into approximately 200 nm thinfilms comprised of five bilayers. Each of these pigments is suitable foruse according to the invention to form a first or second layer of abilayer, either alone or in combination. These pigments may be used, forexample, in blends selected to achieve a bilayer having a relativelyneutral reflection, as defined by its color reflection value. They maylikewise be used alone or in blends to obtain a bilayer that selectivelyblocks light within a wavelength range of interest. They also may eachbe used together with at least two other pigments to obtain a blend thatwhen formed into a bilayer both selectively blocks visible light in awavelength range of interest, while at the same time achieving arelatively neutral reflection, as evidenced by a relatively low colorreflection value. This blend aspect is being separately pursued in acopending application filed herewith having common assignee, thecontents of which are incorporated herein by reference.

It can be seen that each of the five pigments in FIG. 1 exhibits aunique absorption curve, as certain portions of the visible spectrum areabsorbed more strongly than others. When selecting a pigment or pigmentblend that selectively blocks visible light in a wavelength range ofinterest, absorption curves of this type may be used to help select theappropriate pigment. For example, in FIG. 1 it can be seen that theyellow pigment 270Y strongly absorbs in the wavelength range from 400 nmto 450 nm, making it a suitable pigment to block visible light withinthis wavelength range. Similarly, pigment 554B absorbs strongly in thewavelength range from 500 nm to 600 nm, making it a good choice to blockvisible light within this wavelength range.

FIG. 2 depicts the percent of light reflected over the visiblewavelength range for the same thin films for which the absorbance isdepicted in FIG. 1. It can be seen that each of the five pigments inFIG. 2 exhibits a colored reflection, as opposed to a neutralreflection, as certain portions of the visible spectrum are reflectedmore strongly than others. These measured reflective properties may beused as a starting point when creating a pigment blend with suitablereflectance properties. However, the reflectance properties of a givenbilayer, or of the finished optical products of the invention, may alsobe, in part, a function of interference that may also be occurring basedon the thickness of the layers or bilayers and the refractive index ofthe pigment(s). Therefore, a certain amount of routine experimentationmay be helpful when creating a pigment blend to obtain a bilayer havingthe desired neutrality, or color reflection value. Those skilled in theart will be readily able to select suitable pigments or pigment blendsfor use according to the invention using the relevant absorption andreflectance curves.

In FIG. 3 we see that, when three of the five pigments of FIGS. 1 and 2(yellow pigment 270Y, magenta pigment 265M, and cyan pigment 250C) areblended together, in an approximate ratio of 1:1:1 by pigment mass, intoa single layer, no single pigment is dominant, and the bulk reflectionbecomes relatively neutral (sqrt((a*)²+(b*)²)=0.8). This can be seengraphically, since the percent reflection across the visible spectrum isapproximately the same. This is but one example of a pigment blenduseful according to the invention to provide a bilayer having arelatively neutral reflection, as evidenced by its color reflectionvalue.

FIG. 4 depicts the amount of light reflected along the visible spectrumfor 2, 4, 6, and 8 layers of yellow pigment 270Y that is usefulaccording to the invention. It can be seen that increasing theabsorptive ability of a layer-by-layer stack by adding additional yellowlayers will result in a yellow reflection from the surface of thecomposite. However, the reflectance seen may in part be a result ofthin-film interference that is a function of the thickness of a givenlayer or layers, and the refractive index of the pigment. Shown here,incrementally increasing the thickness of a yellow film 2 bilayers at atime, we see the reflected color is not entirely consistent. Adding verythin layers of pigment, for example 2 or 4 bilayers, may serve to reducethis effective reflectance effect. If more layers are desired, minorchanges in formulation, for example of the neutral pigment blend, may behelpful in obtaining an optical product that blocks visible light withina wavelength range of interest while obtaining a suitably neutral colorreflection value.

Thus, the present invention relates to optical products such as windowfilms that include a polymeric substrate, for example PET or PVB,provided with a composite pigment coating, comprising at least one, andpreferably a plurality, of layer-by-layer (LbL) bilayers deposited onthe protective coating, at least one of which layers is or hasincorporated into it a pigment. Each of the layers, as described herein,can be understood to have two faces, a first face and a second face, forthe purpose of describing adjacent layers that each of the layers may bein contact with. Similarly, the finished optical products of theinvention likewise have a first face and a second face, and may ingeneral be applied to an automobile window or architectural window, forexample, in either direction. When measuring a given optical product todetermine whether its properties fall within the scope of the claims,the measurements may be those taken from either direction, and in someaspects of the invention, similar measurements will be obtained fromboth faces, although in other embodiments the desired properties may beobtained only when measured from one direction, and not the other.

Referring now to FIG. 5, a schematic drawing which is not to scale, inone embodiment the present invention relates generally to opticalproducts such as a window film 10. The window film 10 includes apolymeric substrate 15, for example PET, provided with a compositepigment coating 50, comprising a plurality of at least threelayer-by-layer (LbL) bilayers 20, 20′, 20″ deposited on the protectivecoating, each of which layers is or has incorporated into it a pigment.Each of the bilayers 20, 20′ 20″ of the invention is further comprisedrespectively of a first layer 25, 25′, 25″ and a second layer 30, 30′,30″. When used as an exterior or interior window film, the substrate mayadditionally have provided on its bottom an adhesive 5 for adhering thesubstrate to a window.

Referring still to FIG. 5, the multiple bilayers comprise, in sequence:a) at least one bilayer 20 comprised of a neutral pigment or pigmentblend that, when formed into a bilayer, exhibits a color reflectionvalue that is less than about 2.5; b) at least one bilayer 20′ comprisedof a pigment or pigment blend that, when formed into a bilayer,selectively blocks visible light in a wavelength range of interest; andc) at least one bilayer 20″ comprised of a neutral pigment or pigmentblend that, when formed into a bilayer, exhibits a color reflectionvalue that is less than about 2.5, and that may be the same as ordifferent than the pigment or pigment blend of the bilayer a). Accordingto this aspect, the optical product just described selectively blocksvisible light in a wavelength range of interest, while exhibiting arelatively low color reflection value that may be, for example, lessthan about 2.5. This reflectance property may be satisfied when themeasurement is taken of the window film from either direction, or fromboth directions.

As depicted in FIG. 5, each of the bilayers 20, 20′, and 20″, iscomprised respectively of a first layer 25, 25′, and 25″, and a secondlayer 30, 30′, and 30″. According to the invention, either the firstlayer 25, 25′, 25″, or the second layer 30, 30′, 30″, or both the firstand second layer of each bilayer 20, 20′, 20″, will include the pigmentsor pigment blends just described. It will be understood that in thesimplest aspect, the invention comprises three bilayers 20, 20′, and20″, which correspond to bilayers a), b), and c) as just described.However, each or any of these three bilayers may be comprised of morethan one bilayer, so long as the plurality of bilayers satisfies theconditions stated above. Similarly, there may be interposed, between anyor each of these, further bilayers that may be the same as or differentthan those just described, so long as the three bilayers are present inthe stated sequence, and the resulting optical product obtains thedesired color reflectance value. As already noted, additional bilayersd) and e) may optionally be present, as well, and may correspondgenerally to additional bilayers in which bilayer d) is comprised of atleast one bilayer comprised of a pigment or pigment blend that, whenformed into a bilayer, selectively blocks visible light in a wavelengthrange of interest; and bilayer e) comprised of a neutral pigment orpigment blend that, when formed into a bilayer, exhibits a colorreflection value that is less than about 2.5, and that may be the sameas or different than the pigment or pigment blends of other bilayers.

The optical products of the invention may thus be films that aretypically applied to the interior or exterior surface of a window, andpreferably the interior. As noted, these films will be understood tohave two faces, as does each of the layers of which the films arecomprised.

When used as an exterior or interior window film, the substrate mayadditionally have provided on its bottom a means for adhering thesubstrate to a window. The optical product may thus have an adhesivelayer provided on the substrate. The adhesive layer can be comprised ofany adhesive that is suitable for bonding the substrate to a window.When being bonded to a window, pressure sensitive adhesives arepreferable, with an acrylic-based adhesive being particularlypreferable. Loctite Duro-Tak 109A (available from Henkel) is an exampleof such an adhesive. The adhesive layer may also have a release linerattached thereto. The release liner advantageously provides a releaseeffect against the sticky adhesive layer. The release liner in thedepicted embodiment can comprise any polyethylene terephthalate (PET)film with a silicone release coating that can be peeled from theadhesive layer leaving the adhesive layer on the base substrate.Alternatively, the adhesive and release layers may comprise a cleardistortion-free adhesive with a polypropylene liner.

The present invention typically includes a polymeric substrate,preferably a film formed from a thermoplastic such as a polyester andpreferably polyethylene terephthalate (PET). Suitable PET films arecommercially available, for example from DuPont Teijin Films under thenames Melinex 454 or LJX 112. Other suitable thermoplastics for formingthe polymeric substrate include, for example, polyvinyl butyral,polyacrylic, polyimides, polyamides such as nylons, and polyolefins suchas polyethylenes, polypropylenes and the like. The polymeric substratemay include conventional additives such as UV-absorbers, stabilizers,fillers, lubricants and the like, blended therein or coated thereon.Preferably, the polymeric substrate is transparent, which generallyconnotes the ability to perceive visually an object, indicia, words orthe like through it.

The polymeric substrate may in the broadest sense be any substrate knownin the art as useful as an optical product component. A suitablepolymeric substrate is typically a flexible thermoplastic polymericfilm, more particularly a polyethylene terephthalate (PET) film of athickness, for example, from about 10μ to about 400p, or from 15μ to300p, or from 20μ to 250μ; or a polyvinyl butyral (PVB) film, preferablyof a thickness from 0.01 to 1 mm, or from 0.05 to 0.5 mm, or from 0.1 mmto 0.45 mm, and more preferably a thickness of 15 to 30 mils. Becausewindow films that employ dyes exhibit a variety of drawbacks, thepolymeric substrate is preferably an undyed transparent polyethyleneterephthalate film. The term “undyed” means that the raw film has noappreciable color, and is not intended to exclude the presence ofadditives such as UV blockers that are present in small amounts and notintended to affect the appearance of the film. The polymeric substratemay also be a flexible polyurethane or flexible poly(vinyl chloride)film or may be a flexible multilayer polymeric composite film such as apolyurethane-based multilayer composite film as described for example inU.S. Pat. No. 8,765,263, the disclosure of which is incorporated hereinby reference.

The polymeric substrate may further include additives known in the artto impart desirable characteristics. Examples include ultraviolet (UV)absorbing materials such as benzotriazoles, hydroxybenzophenones ortriazines. A useful polymeric substrate with a UV absorbing additiveincorporated therein is described in U.S. Pat. No. 6,221,112, which isincorporated herein by reference.

In one embodiment, wherein the polymeric substrate is a flexiblepolymeric film such as PET, the optical product may be a window film. Aswell known in the art, conventional window films are designed andmanufactured with levels of electromagnetic energy transmittance orreflectivity that are selected based on a variety of factors such as,for example, product end-use market applications, and the like. In somesettings, the desired optical properties include maximum rejection(reflection) of infrared wavelengths with less attention being paid tothe amount of visible light transmitted or reflected. In otherapplications, specific degrees of visible light transmittance must beattained to meet government regulations, for example, in autowindshields in which regulations may require that the T_(vis) be 70% orgreater. According to the present invention, the optical products of theinvention selectively block visible light in a wavelength range ofinterest, while exhibiting a relatively neutral color reflection.

The visible light transmission (VLT or T_(vis)) is the spectraltransmission in which the effect of each wavelength across the visiblespectrum is weighted according to the eye's sensitivity to thatwavelength. That is, it is the amount of light that is “seen” to betransmitted through the window film/glass system. The lower the number,the less visible light transmitted. It may be calculated using CIEStandard Observer (CIE 1924 1931) and D65 Daylight. As noted, theoptical products of the present disclosure may have a visible lighttransmission within a broad range of VLT values, depending on thedesired transparency, for example less than about 1%; from about 2% toabout 5%; from about 25% to about 50%; about 28.5% to about 47%; about30% to about 45%; about 28.5%; about 47%; about 55%; up to about 70%; orup to about 75%, or up to about 90%, or as described elsewhere herein.

In other embodiments, the optical product of the present invention mayhave visible light transmittance (T_(vis) or VLT) of no more than 50%,or no more than 45% or no more than 40%. Such levels of visible lighttransmittance are often desired in window films with high levels ofdarkening for certain automotive end use applications such assidelights.

In another embodiment, the optical product of the present invention hasvisible light transmittance or T_(vis) of from 80 to 85%. Such levels ofvisible light transmittance are often desired in window films withrelatively moderate to low levels of darkening (typically also withinfrared absorption) for (to the extent permitted by governmentalregulation) certain automotive end use applications such as windscreens.In yet another embodiment, the optical product of the present inventionhas visible light transmittance or T_(vis) of no less than 85%, or noless than 88% or no less than 90%. Such levels of visible lighttransmittance are often desired in window films with low to minimallevels of darkening for certain architectural end use applications.These various levels of visible light transmission may be achievedaccording to the invention through a reduction in visible lighttransmission achieved by the composite pigment coating.

The window films may optionally include further layers or coatings,other than any protective coating layer and the composite pigmentcoating, that are known to those of ordinary skill in the window filmart. Coatings, for example, may include adhesive layers, protectiverelease liners, and the like, as described herein. Such layers orcoatings may be components of the polymeric substrate. Further, thepolymeric substrate may be a laminated or multilayer structure.

In another embodiment, the optical product is an interlayer forlaminated glass. In this embodiment, the polymeric substrate is formedfrom or afterward bonded to a film-forming material known in the art forthis purpose, including for example plasticized polyvinyl butyral (PVB),polyurethanes, polyvinyl chloride, polyvinylacetal, polyethylene, ethylvinyl acetates and the like. A preferred film-forming material for theinterlayer is a plasticized PVB such as that used in a commerciallyavailable product from Eastman Chemical Company, SAFLEX® PVB interlayer.In this embodiment, the composite coating may be formed on at least onesurface of the polymeric substrate.

In an embodiment wherein the substrate is a flexible polymeric film suchas PET, the optical product may be a composite interlayer for laminatedglass including at least one safety film or interlayer. The safety filmmay be formed from film-forming materials known in the art for thispurpose, including, for example, plasticized polyvinyl butyral (PVB),polyurethanes, polyvinyl chloride, polyvinylacetal, polyethylene, ethylvinyl acetates and the like. The safety film may be a plasticized PVBfilm or interlayer commercially available from Eastman Chemical Companyas SAFLEX® PVB interlayer. The composite interlayer may include twosafety films or one film layer and one coating layer, such as a PVBcoating, that encapsulate the polymeric substrate. Composite interlayersof this general type are known in the art and are described for examplein U.S. Pat. Nos. 4,973,511 and 5,091,258, the contents of which areincorporated herein by reference.

The polymer substrates described herein may thus include one or morethermoplastic polymers. Examples of suitable thermoplastic polymers caninclude, but are not limited to, poly(vinyl acetal) resins (such asPVB), polyurethanes (“PU”), poly(ethylene-co-vinyl)acetates (“EVA”),polyvinyl chlorides (“PVC”), poly(vinyl chloride-co-methacrylate),polyethylene, polyolefins, ethylene acrylate ester copolymers,poly(ethylene-co-butyl acrylate), silicone elastomers, epoxy resins, andacid copolymers such as ethylene/carboxylic acid copolymers and ionomersthereof, derived from any of the previously-listed polymers, andcombinations thereof. In some embodiments, the thermoplastic polymer canbe selected from the group consisting of poly(vinyl acetal) resins,polyvinyl chloride, and polyurethanes, or the resin can comprise one ormore poly(vinyl acetal) resins. Although some of the polymer layers maybe described herein with respect to poly(vinyl acetal) resins, it shouldbe understood that one or more of the above polymer resins and/orpolymer layers including the polymer resins could be included with, orin the place of, the poly(vinyl acetal) resins described below inaccordance with various embodiments of the present invention.

When the polymeric substrates described herein include poly(vinylacetal) resins, the poly(vinyl acetal) resins can be formed according toany suitable method. Poly(vinyl acetal) resins can be formed byacetalization of polyvinyl alcohol with one or more aldehydes in thepresence of an acid catalyst. The resulting resin can then be separated,stabilized, and dried according to known methods such as, for example,those described in U.S. Pat. Nos. 2,282,057 and 2,282,026, as well asWade, B. 2016, Vinyl Acetal Polymers, Encyclopedia of Polymer Scienceand Technology. 1-22 (online, copyright 2016 John Wiley & Sons, Inc.).The resulting poly(vinyl acetal) resins may have a total percentacetalization of at least about 50, at least about 60, at least about70, at least about 75, at least about 80, at least about 85 weightpercent, measured according to ASTM D1396, unless otherwise noted. Thetotal amount of aldehyde residues in a poly(vinyl acetal) resin can becollectively referred to as the acetal component, with the balance ofthe poly(vinyl acetal) resin being residual hydroxyl and residualacetate groups, which will be discussed in further detail below.

The polymeric substrates according to various embodiments of the presentinvention can further include at least one plasticizer. Depending on thespecific composition of the resin or resins in a polymer layer, theplasticizer may be present in an amount of at least about 5, at leastabout 15, at least about 25, or at least about 35, or at least about 50,parts per hundred parts of resin (phr) and/or not more than about 120,not more than about 100, not more than about 90, not more than about 75,not more than about 70, or not more than about 55, not more than about50, not more than about 45, or not more than about 40 phr, or in therange of from about 5 to about 120, about 10 to about 110, about 20 toabout 90, or about 25 to about 75 phr.

As used herein, the term “parts per hundred parts of resin” or “phr”refers to the amount of plasticizer present as compared to one hundredparts of resin, on a weight basis. Further, when the plasticizer contentof a polymer layer is provided herein, it is provided with reference tothe amount of plasticizer in the mix or melt that was used to producethe polymer layer.

In another aspect, the present invention is directed to methods forforming optical products. In one embodiment, the method of the presentinvention includes applying to the protective layer a composite pigmentcoating. The composite pigment coating may be applied to the protectivelayer by applying a first layer to the protective layer and thereafterapplying a second layer to form a bilayer. The process is then repeateduntil the desired number and nature of bilayers is achieved. The firstlayer of the bilayer may include a polyionic binder and/or a pigment,and the second layer may likewise include a binder and/or a pigment,with each of the first and second layers including a binding groupcomponent which together form a complementary binding group pair. Atleast one of the layers, and especially those layers that include acharged pigment particle, may include a screening agent as definedabove.

In a preferred embodiment, at least one of the first and second layersare applied as an aqueous dispersion or solution and most preferablyboth of the first and second layers are an aqueous dispersion orsolution. In this embodiment, both applying steps (a) and (b) areperformed at ambient temperature and pressure.

The optical products of the present invention are thus preferablymanufactured using known “layer-by-layer” (LbL) processes such asdescribed in Langmuir, 2007, 23, 3137-3141 or in U.S. Pat. Nos.8,234,998, 8,689,726 and 9,387,505, co-invented by co-inventor Krogmanof the present application, the disclosures of which are incorporatedherein by reference.

The following examples, while provided to illustrate with specificityand detail the many aspects and advantages of the present invention, arenot be interpreted as in any way limiting its scope. Variations,modifications and adaptations which do depart of the spirit of thepresent invention will be readily appreciated by one of ordinary skillin the art.

The light measurements, as used herein, are calculated using the 1976CIE L*a*b* Color Space convention, and were measured using aPerkin-Elmer Lambda 900 UV-Vis-NIR Spectrometer.

EXAMPLES

In Examples 1-3, we describe three techniques for constructing a filmwhich blocks approximately 80% of blue light (between 400 and 450 nm, awavelength range of interest of 50 nm), but only about 60% in theremainder of the spectrum. Employing an interleaved structure (Ex.1)results in a product which is substantially neutral in reflection,whereas grouping and separating the neutral and accent layers (Ex. 2 andEx. 3) produces a colored reflection.

Example 1

To form the optical product of the present invention, a sheet ofpolyethylene terephthalate (PET) film (as substrate) with a thickness of75 microns was pretreated as known in the art by passing through aconventional corona treatment. A first layer was then formed on the PETsheet by spray coating, at ambient pressure and temperature, a firstcoating composition of 20 mM solution, based on the molecular weight ofthe charged repeat unit, of polyallylamine hydrochloride with anadjusted pH of 9.5, as further described below. Excess non-absorbedmaterial was rinsed away with a deionized water spray. A composition foruse in forming the second layer, as described below, was then sprayedonto the surface of the first layer with excess material again rinsedaway in a similar fashion.

In this example, the first coating composition for the first layer ofthe optical product was formed by dissolving 0.94 g of poly(allylaminehydrochloride) per liter of deionized water, and titrating the pH of theresulting solution to 9.5 using sodium hydroxide. A neutral secondcoating composition for forming the second layer of a neutral compositelayer, a 0.5 wt % solids pigment blend dispersion of 6.07 g Cab-o-Jet352K black, 10.85 g Cab-o-Jet 250C cyan, and 15.05 g Cab-o-Jet 265Mmagenta pigments in 1 L of distilled water, was also formed, with 2.92 gof sodium chloride added as screening agent to ionically screen thecolloidal particles and prepare them for deposition. The 352K blackpigment has ionizable carboxylate functionality at its surface while the250C cyan pigment and 265M magenta pigment have ionizable sulfonatefunctionality at their respective surfaces. Titrating the second coatingcomposition to pH 7.5 produces a scenario where approximately 75% of theCab-o-Jet 352K black pigment ionizable carboxylate functionalities areionized to form negative carboxylate groups, while 25% are not ionizedand are present as carboxylic acids. This was found empirically toreduce the charge density on the black pigment to more closely match thesulfonate charge density on the cyan and magenta pigments. The aboveprocedure may then be utilized to form an optical product with the firstlayer from the first composition above and a second layer formed fromthe pigment blend-containing second coating composition described above.This deposition process may be repeated for the substrate multiple timesto deposit multiple composite coatings on the substrate and achieveincreasing coloration with each repetition.

Similarly, another second coating composition for forming the secondlayer of an “accent” or “blocking” composite layer, a 0.5 wt % solidspigment dispersion of 35.0 g Cab-o-Jet 270Y yellow pigment in 1 L ofdistilled water, is also formed, with 2.92 g of sodium chloride added asscreening agent to ionically screen the colloidal particles and preparethem for deposition. An optical product is created by repeating theabove procedure seven times using the first coating composition and theneutral second coating composition, followed by three times using thefirst coating composition and the accent second coating composition,followed by two times using the first coating composition and theneutral second coating composition, thereby forming a coating which isPET/7 layers black/3 layers yellow/2 layers black. The reflection andtransmission of the composite coating were then measured using a UV-visspectrometer, the results of which are depicted graphically in FIGS. 6and 7 respectively.

Example 2

Using the same coating compositions from Example 1, an optical productwas created by repeating the above procedure nine times using the firstcoating composition and the neutral second coating composition, followedby three times using the first coating composition and the accent secondcoating composition, thereby forming a composite coating which is PET/9layers black/3 layers yellow. The reflection and transmission of theoptical product were then measured using a UV-vis spectrometer, theresults of which are depicted graphically in FIGS. 6 and 7 respectively.

Example 3

Using the same coating compositions from Examples 1 and 2, an opticalproduct is created by repeating the above procedure three times usingthe first coating composition and the accent second coating composition,followed by nine times using the first coating composition and theneutral second coating composition, thereby forming a composite coatingwhich is PET/3 layers yellow/9 layers black. The reflection andtransmission of the optical product were then measured using a UV-visspectrometer, the results of which are depicted graphically in FIGS. 6and 7 respectively.

It can be seen that the transmission measurements of all three films arequite similar because they contain the same quantities of absorptivepigments, and as such produce similar transmitted color. Reflectionmeasurements, however, indicate the distinctly different colorreflection values of the three composite coatings.

TABLE 1 Transmission Reflection Example No. a* b* a* b* neutrality 1−6.47082 14.86763 0.284662 −0.19185 0.34327505 2 −6.42574 14.357740.127561 −10.7046 10.7053715 3 −6.41008 14.18304 2.408377 4.6273195.21654675

It can be seen from Table 1 that all three coatings show the stronglypositive b* value indicative of very yellow transmission, but only theinterleaved structure of Example 1 is appreciably neutral in reflection.Ex.2 produces a coating which is quite blue in reflection, and Ex. 3produces one which is strongly yellow/red in reflection.

In Examples 4 and 5, we describe two techniques for constructing a filmwhich selectively blocks red light using cyan pigment. Employing aninterleaved structure (Ex. 4) results in a product which issubstantially neutral in reflection, whereas grouping and separating theneutral and accent layers (Ex. 5) produces a colored reflection.

Example 4

Another second coating composition for forming the second layer of anaccent or blocking composite layer, a 0.5 wt % solids pigment dispersionof 35.0 g Cab-o-Jet 250C cyan pigment in 1 L of distilled water wasformed, with 2.92 g of sodium chloride added as screening agent toionically screen the colloidal particles and prepare them fordeposition. An optical product was created by repeating the procedure ofExample 1 seven times using the first coating composition and theneutral second coating composition, followed by three times using thefirst coating composition and the accent second coating compositioncontaining the cyan pigment, followed by two times using the firstcoating composition and the neutral second coating composition, therebyforming a coating which is PET/7 layers black/3 layers cyan/2 layersblack. The reflection and transmission of the composite coating werethen measured using a UV-vis spectrometer, the results of which aredepicted graphically in FIGS. 8 and 9 respectively.

Example 5

Using the same coating compositions from Example 4, an optical productwas created by repeating the above procedure nine times using the firstcoating composition and the neutral second coating composition, followedby three times using the first coating composition and the accent secondcoating composition containing cyan pigment, thereby forming a compositecoating which is PET/9 layers black/3 layers cyan. The reflection andtransmission of the composite coating were then measured using a UV-visspectrometer, the results of which are depicted graphically in FIGS. 8and 9 respectively.

The transmission measurements of the two films are quite similar becausethey contain the same quantities of absorptive pigments, and as suchproduce similar transmitted color. The reflection measurements, however,indicate the distinctly different color reflection values of the twocomposite coatings.

TABLE 2 Transmission Reflection Example No. a* b* a* b* neutrality 5−12.2317 −12.9912 10.95137 3.34545 11.4509576 4 −12.0144 −13.93670.475119 −0.79703 0.92789691

It can be seen from Table 2 that both coatings show the stronglynegative a* and b* values indicative of blue/green transmission, butonly the interleaved structure of Example 4 is appreciably neutral inreflection. Ex.5 produces a coating which is quite red in reflection.

A person skilled in the art will recognize that the measurementsdescribed herein are measurements based on publicly available standardsand guidelines that can be obtained by a variety of different specifictest methods. The test methods described represent only one availablemethod to obtain each of the required measurements.

The foregoing description of various embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the preciseembodiments disclosed. Numerous modifications or variations are possiblein electromagnetic energy of the above teachings. The embodimentsdiscussed were chosen and described to provide the best illustration ofthe principles of the invention and its practical application to therebyenable one of ordinary skill in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the invention as determined by the appended claimswhen interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

We claim:
 1. An optical product comprising a composite coating,deposited on a substrate, that includes multiple bilayers having a firstlayer and a second layer, each provided with a binding group componentwhich together form a complementary binding group pair, the multiplebilayers comprising, in sequence: at least one bilayer a) comprised of afirst pigment or pigment blend that, when formed into a bilayer,exhibits a color reflection value that is less than about 2.5; at leastone bilayer b) comprised of a pigment or pigment blend that, when formedinto a bilayer, selectively blocks visible light in a wavelength rangeof interest; and at least one bilayer c) comprised of a second pigmentor pigment blend that, when formed into a bilayer, exhibits a colorreflection value that is less than about 2.5, and that may be the sameas or different than the first pigment or pigment blend, wherein theoptical product selectively blocks visible light in the wavelength rangeof interest, while exhibiting a color reflection value that is less thanabout 2.5.
 2. The optical product of claim 1, wherein the wavelengthrange of interest is a 75 nm wavelength range.
 3. The optical product ofclaim 1, wherein the wavelength range of interest is a 50 nm wavelengthrange.
 4. The optical product of claim 1, wherein the wavelength rangeof interest is from 400 nm to 450 nm.
 5. The optical product of claim 1,wherein the wavelength range of interest is from 600 nm to 650 nm. 6.The optical product of claim 1, wherein the wavelength range of interestis from 500 nm to 600 nm.
 7. The optical product of claim 1, wherein thewavelength range of interest is from 525 nm to 575 nm.
 8. The opticalproduct of claim 1, further comprising: at least one bilayer d),deposited on the at least one bilayer c), comprised of a pigment orpigment blend that, when formed into a bilayer, selectively blocksvisible light in the wavelength range of interest, and that may be thesame as or different than the pigment or pigment blend of bilayer b);and at least one bilayer e) comprised of a neutral pigment or pigmentblend that, when formed into a bilayer, exhibits a color reflectionvalue that is less than about 2.5, and that may be the same as ordifferent than the pigment or pigment blend of bilayer a) or bilayer c).9. The optical product of claim 1, wherein the color reflection value isless than about 2.0.
 10. The optical product of claim 1, wherein thecolor reflection value is less than about 1.5.
 11. The optical productof claim 1, wherein the optical product blocks at least 70% of visiblelight within the wavelength range of interest.
 12. The optical productof claim 1, wherein the optical product blocks at least 80% of visiblelight within the wavelength range of interest.
 13. The optical productof claim 1, wherein the substrate comprises a polyethylene terephthalatefilm.
 14. The optical product of claim 1, wherein the composite coatinghas a total thickness of 5 nm to 1000 nm.
 15. The optical product ofclaim 1, in the form of a window film that is applied to a vehicle. 16.The optical product of claim 13, wherein the vehicle is an automobile,an aircraft, or a boat.
 17. The optical product of claim 1, in the formof a window film applied to a building.
 18. The optical product of claim2, wherein the optical product is a composite interlayer for laminatedglass.
 19. The optical product of claim 16 wherein said optical producthas a visible light transmission of no less than 40%.
 20. The opticalproduct of claim 16, wherein said optical product has a visible lighttransmission of no less than 60%.